The present invention relates generally to the field of light influencing elements for use in high resolution optical systems, and particularly to a method of making such elements. The invention more particularly relates to light influencing elements adapted to act as a color filter for optical systems such as image scanning systems and active or passive liquid crystal display devices. In it""s most specific form, the instant invention relates to high resolution color filter elements, and methods of making the same, which are adapted to all or pan of a liquid crystal display device, such as an active matrix liquid crystal display, disposed thereupon.
Efficient production of full color systems for use in cameras, television, etc. have been contemplated since at least as early as the late 1950""s and are generally discussed in an article which appeared in the May 1959 edition of Scientific American. Reference may also be made to U.S. Pat. Nos. 3,382,317, 3,443,023 and 3,443,025. As optical system technology evolved, so too did the technology employed in providing full color thereto.
High resolution electronic optical systems, such as for example, either active or passive liquid crystal displays, and contact image scanning systems are today well known in the commercial fields. While systems of the type described above have been generally successful in fulfilling their intended purposes and have found commercial acceptance, these systems exhibit several deficiencies. The deficiency specifically addressed herein relates to the fact that heretofore, the light influencing elements used in high resolution optical systems, to, for example, polarize or color filter light passing therethrough, have been very difficult to fabricate, often requiring up to ten or more fabrication steps. The result of having so many fabrication steps is that the manufacturing process is very costly, and further that the process is susceptible to producing high amounts of unacceptable or scrap light influencing elements. This of course further increases the cost of the light influencing elements.
As noted above, color liquid crystal display devices are well known in the art, and one exemplary such device is set forth in U.S. Pat. No. 4,632,514 to Ogawa, et al, entitled xe2x80x9cCOLOR LIQUID CRYSTAL DISPLAY APPARATUSxe2x80x9d. The ""514 patent describes a color, twisted nematic type display wherein the layer of liquid crystal material is varied depending upon the color imparted to each picture element of the display. Ogawa, et al describe the need to terrace the layers of filter materials, which, as will be noted in greater detail hereinbelow, require additional fabrication steps in the manufacture of a display.
The commonly accepted method of fabricating light influencing elements for high resolution optical systems, particularly liquid crystal displays, is set forth in an article entitled Multicolored Liquid Crystal Displays, published in Optical Engineering, Vol. 23 No. 3, May/June 1984. More particularly, FIG. 11 thereof illustrates in a step-by-step manner, the conventional photolithographic method of fabricating color filter elements for liquid crystal display. As a perusal of said article teaches, a color filter element is fabricated by depositing a layer of transparent gelatine glue, known in the art as xe2x80x9cfish gluexe2x80x9d atop the display electrodes, which have already been formed upon a transparent substrate. A photomask is then applied so that the transparent gelatine glue is removed from all ares other than atop a display electrode. Thereafter, a layer of photoresist material is disposed atop the entire device substrate and a photomask is applied so that, assuming a red-green-blue color filter arrangement, all electrodes and gelatine layers to be colored red are exposed, while the electrodes to be colored blue or green remain covered by photoresist. The exposed gelatine glue is then dyed red and the dye is cured. Thereafter, the photoresist is removed from the electrodes to be dyed green and blue, and a new layer of photoresist is applied over the entire device substrate, and a photomask is applied to expose the electrodes to be colored blue. The exposed gelatine glue is then dyed blue and the dye is cured. The same process is then repeated to provide the green dyed electrodes.
An alternative, dry-etching technique is set forth in an article entitled Fabrication of mosaic color filters by dry-etching dielectric stacks, Journal of Vacuum Science Technology, A4(1), Jan/Feb 1986. The approach is illustrated fully in FIG. 3 thereof, which clearly illustrates the need to etch, mask and re-etch the deposited materials in order to achieve the desired color configuration. Moreover, this approach is limited to certain color combinations and arrangements as two or more filter layers may be needed to produce a single color.
A third commonly accepted method of providing color filter materials is set forth in an article entitled Multicolor Graphic LCD with tricolor layers formed by electrodeposition, and published in the 1984 Society for Information Display Digest. In this article, the authors set forth an electrodeposition method for depositing and patterning color filter layers. In this method, certain electrode layers were activated so as to cause dyed pigments to be electrochemically deposited thereupon. Thereafter, a second set of electrodes is activated so that a second color can be deposited, and so on for all subsequent colors to be deposited. While this method does not require the deposition and patterning of filter material layers, it does require the deposition and patterning of electrode layers, and the subsequent electrodeposition steps for each color.
In addition to the deficiencies inherent in the multistep deposition/etch processes discussed hereinabove, none of such methods of fabricating a light influencing element provide a light barrier around each color filter so as to eliminate the presence of stray, non-filtered light. Such stray, non-filtered light has the effect of washing out the color of the light that is being transmitted through the color filter. The result is that the color image looses sharpness and intensity. A light blocking layer around color filters or display picture elements is commonly called a black matrix in the field. The provision of a black matrix has heretofore involved the subsequent deposition of a light blocking layer of material around the filters or the picture elements after such elements have been formed. The result is the need to provide additional photoresist deposition, mask and etch steps in order to provide the black matrix, with the most often result being greater expense attributable to more costly processing and greater losses cause by the manufacturing process itself.
These and other limitations of the prior art are obviated by the invention disclosed and claimed herein.
It is an object of the present invention to provide a light influencing element for high resolution electronic optical systems, and a method of fabricating the same which avoids the need to employ repeated photolithographic steps.
It is a further object of the instant invention to provide a light influencing element which also includes a black matrix layer for improving the contrast, resolution and sharpness of optically enhanced light passing therethrough.
It is a further object of the instant invention to provide liquid crystal display devices and subassemblies thereof which may be fabricated upon the light influencing element of the instant invention.
These and other objects are achieved by fabricating light influencing elements which by a comprising the steps of: providing a substantially transparent substrate member, disposing a layer of a substantially opaque material upon one side of said substrate; forming at least one opening through said layer of substantially opaque material; and disposing a light influencing material in said at least one opening. The substantially transparent substrate member is typically selected from the group of materials consisting of glass, plastic and combinations thereof.
The layer of substantially opaque material is disposed to a thickness of between 0.10 and 100.0 xcexcm, and preferably between 1.0 and 10.0 xcexcm. This opaque material may be fabricated from a deposit of materials such as a polymeric material, metallic materials, semiconductor materials and combinations thereof, though in a preferred embodiment, the material is a black polyimide material.
One or more openings or wells are formed through said layer of substantially opaque material. The formation of such openings is accomplished by employing a method such as a high power laser, or a photolithographic etch process to cut or eat away the opaque material. When the embodiment of a laser is employed, a high power excimer laser capable of at least micron scale resolution is required to be placed in close proximity to said substrate and layer of opaque material. Depending upon the application desired for the light influencing element, a plurality of similarly sized and shaped vias arranged in a densely packed, uniformly spaced Mxc3x97N array may be provided. Alternatively, the array of vias may be arranged into a series of interlocking triangles or xe2x80x9ctriadsxe2x80x9d, or elongated stripes.
Into the opening or openings is disposed a light influencing materials as by providing a light influencing material in non-solid phase having the optical characteristics thereof optimized for the desired application, which material is injected in a sufficient amount so as to achieve a desired light influencing effect. Thereafter, the material is curing from the non-solid to the solid phase.
In one embodiment, the light influencing element is adapted to function as a color filter element for a liquid crystal display or a subassembly thereof. In this application, the light influencing material is adapted to color white light into the group of colors consisting of red, green, blue and combinations thereof.
These and other objects and advantages of the subject invention will become apparent from a perusal of the detailed description of the invention, the drawings and the claims which follow.